The present teachings are related to the conversion of kinetic energy existing in various flows, such as an airflow, a water flow, a tidal wave, etc., into electricity. The present teachings describe a novel energy converter, and its various embodiments, that efficiently utilizes oscillations induced by different types of flow, in order to generate electricity.
Mankind has been utilizing the flow energy of water or wind for centuries. The kinetic energy of a flow can be converted into rotating or oscillating movements of the affected device, where energy can further be harvested by different means.
Modern wind-powered and hydro-powered generators that are based on propellers, rotors, turbines, or rotating airfoils became reliable and widespread energy sources and their implementations are growing due to their economical power production and environmental benefits.
Large wind turbines, which are typically located off shore or in remote areas, have increasingly being installed worldwide, providing megawatts of electric power without polluting the environment. Although the turbine-based wind generators are, in general, effective in certain conditions, they have limitations resulting from typical requirements of large open spaces (consistently high-speed winds), infrastructure development requirements and large initial capital costs.
While such generators can provide sufficient energy for small applications, they are not optimized for efficient conversion of energy available in various flows of gases or fluids.
The previous designs of flow energy harvesting devices require incorporation of weights, in forms of coils or magnets, and vortex shading devices designed to move a substantial mass with some displacements at a certain frequency. This mass requires a special vibrating assembly and, in some cases, a source of instability at the oscillation onset. This limits the span of possible oscillation frequencies and/or may damp down the desired oscillation frequencies for certain flow characteristics. Moreover, in all previously proposed generators the weight of the vibrating element restricts the allowed transducer geometry, resulting in a limited range of oscillation frequencies needed for efficient energy conversion. Accordingly, previously disclosed vibration-based power generators are not optimized to utilize the available energy of various flows in a single vibrating assembly, thus limiting the energy conversion efficiency.
Vibration-based electro-mechanical converters are facing another problem associated with achieving efficient rectification of the generated alternating current (AC). Different attempts have been made to optimize the energy extraction from the generators by improving the rectifying electrical circuits.
Therefore, there is a strong need for a new type of low-cost/low-maintenance power generators that are capable of efficient conversion of the flow kinetic energy into electricity under various conditions, such as flow velocities, temperature/humidity variations, etc. New, commercially feasible, small foot-print, scalable solutions are needed to overcome the previous rationales that restrained the non-turbine electrical generators from earlier implementation.
The growing emergence of microwatt to milliwatt motional/vibrational energy harvesting technology is promoting the development of low-power power management circuits. For vibrational energy harvesters, one specific need is in ac/dc converter circuits that can operate at low input power and low voltage with acceptable efficiency (usually greater than 80%). However, so far most attention has been focused on circuits for piezoelectric harvesters, where output voltage levels are generally higher (typically greater than 1 V) than in similarly sized magnetic harvesters (typically less than 1 V). No suitable low-voltage rectification solution exists currently for an effective implementation of the harvesting systems of the present teachings. Therefore, the present teachings also contain a disclosure of a compatible rectification solution.